+1 to the Set, Map, IntMap, etc., performance improvements. The style
consistency is probably a good concomitant effect. Testsuite and
benchmark make sense in concept too (I haven't looked at the code, I
trust that it's fine). Good job!
Antoine's "Is this sort of optimization specific to the way GHC compiles
things, or will other compilers likely either benefit or not care?" is
an interesting question that I'd be curious to hear about. (does
Criterion work on non-GHC?). but that in my judgment shouldn't delay
these particular patches.
-Isaac